Management systems, e.g., in the form of electronic circuit boards comprising software that is integrated accordingly, may be used for monitoring, controlling and measuring rechargeable chemical energy storage devices in various fields of application. Said management systems will be referred to below as battery management systems (abbreviation: BMS). One example of a chemical storage device are lithium ion batteries, which are becoming more and more attractive due to their high energy density.
Since individual battery cells mostly have only very small voltages—lithium ion battery cells have a nominal voltage of 3.6 V, for example—battery cells are electrically connected in series to achieve higher voltages. Moreover, it is highly useful to connect them in parallel to increase capacitance. Such clusters are referred to as battery systems. It is recommendable to monitor said clusters of cells by means of a BMS since otherwise overcharging and exhaustive discharges may occur during charging and discharging, respectively. In the worst case, this may cause a battery cell to explode. In addition, it may be important for various reasons to know the current states of charge of the individual battery cells as well as their temperatures. Furthermore, it should be possible to create appropriate connections at the system level, a cooling system for the battery system may be used in order to be able to provide higher powers. For monitoring such battery systems, a BMS itself involves energy supply. Said energy supply may be configured to be correspondingly efficient and reliable.
In conventional technology concerning energy supply for a BMS, the entire electronics or at least a circuit part of the BMS is supplied with energy directly from the battery cells to be monitored DE102008052986, EP2204874, DE102011079292, EP2549581. The other circuit part is supplied, alternatively, from an external energy source or, in the case of grid-independent systems, also from the battery cells to be monitored. This results in that due to its own energy consumption, a BMS may exhaust a battery system or an individual battery cell. This may occur particularly when the battery system is not charged for a long time. For example, an electric vehicle that sits in the garage without receiving any energy supply for several weeks during the summer holidays. In the event of repair works or of being stored for several months, the BMS may be mechanically separated from the battery.